System of radio or television broadcasting or transmission



March 2, 1954 G|LPIN ET AL 2,671,165

SYSTEM OF RADIO 0R TELEVISION BROADCASTING OR TRANSMISSION Filed Feb. 16, 1950 3 Sheets-Sheet 2 ATTORNEY March 2, 1954 Filed Feb. 16, 1950 arc/Area j PULSE I OJcumrmt 81. our: Na

451545: Paws L. H. SYSTEM OF RA GILPIN ET AL DIO OR TELEVISION BROADCASTING OR TRANSMISSION 3 Sheets-SheeiS arc/Aron. l J6 1 I 1 l 5 8 PfiL ournws 51:12: (43

BLfCK /G Puss;

I l l INVENTORS [Evie/N671. G/LP/N HERMAN L. Guano/v ATTORNEY Patented Mar. 2, 1954 CASTING R T Levering H. Gilpin, Washington,

man L. Gordon,

TELEVISIONBROAD- RANSMISSION D. 0., and Her- Silver Spring, Md assignors to Gilpin Electronics Inc., corporation of Delaware Washington, D. 0., a

Application February 16, 1950, Serial No. 144,526

4 Claims.

This invention relates to radio and television broadcasting systems, and more particularly to I radio or television transmitting and receiving system wherein entertainment programs may be Iunanated from advertising or other undesirable materialby the automatic operation of means in the receivers, responding to control signals in the transmission.

A mam oln'ect of. the invention is to provide a novel and'improved system of radio broadcasting and reception. wherein entertainment programs, such as music or the like, may be provided to ers, with no commercial announcements muncements are not eliminated in the case of nomsubscribers receiving the program.

A further object of the invention is to provide on improvedsystem whereby a radio broadcasting station or radio transmitter of the AM, PM or television type may transmit aprogram consistis: of various material, such as music, speech, monuments, news, advertising, etc, and by the use of special receivers, described hereafter, emblcsthe transmitter to predetermine and controlwhat portion or parts of the total program the special receivers will reproduce at various times during any period of time.

A still l urther object of the invention is to provide an improved system of broadcasting of the above character, wherein variable coded sigads are employed in the transmission to control in special receivers, the coded signals being my changed from tlmeto time in such mannor us-to make it impossible for receivers other flunthe special receivers of the system to respond thine coded signals.

A still" further object oi the invention is to provide an improved broadcasting system wherem coded signals are employed to control special receivers, the signals being of such character as to make their detection very dlfficult, and the coding being variable in a very simple and efi'etiti've manner, so that those who are not subscribers to the System will have great difllculty in enjoying its benefits.

Further objects and advantages of the invention willbecome apparent from the following description and claims, and from the accompanying m'awlngs, wherein:

Figure 1 is a block diagram illustrating a transmitter coding arrangement according to the presemanation,

Figure 2 is a graph illustrating the shape of the envelope of the coding signal obtained by the apparatus of gure 1'.

Figure-3 is a schematic diagram of a special receiver arranged to respond to the codin'gisignal of Figures 1 and 2.

Figure 4 is a graph illustrating a modified form of coding signal'employed in accordance with the present invention.

Figure 5 is aschematic diagram illustrating one form of transmitter: coding arrangement adapted to provide the coded signal of Figure 4,

Figure 6 is a schematic diagram of a special receiver arranged to respond to the coded signal of Figure 4.

Figure 7 is a schematic diagram of a more generalized form of transmitter coding arrangement adapted to provide "a coded signal.

Figure 8 is a graph illustrating the generalized coded signal obtained by the arrangement of Figure '7;

Figure 9 is aschemat'ic view illustrating a modified form of pulsing commutator which maybe employed in the arrangement of Figures 5 or 7 in accordance with the present invention.

Figure 10 is a graph illustrating the coding signal obtained by the use of the pulsing commutator of Figure 9.

Figure 11 is a side 'elevational view of a variable-speed pulsing motor which may be employed in driving the pulsing commutator ofthe system illustrated in Figures 5, 7 or 9.

Figure 12 is a diagrammatic end elevational view of the variable-speed pulsing motor of Figure 11.

Figure 13 is a diagrammatic view showing the punch-oard frequency-selecting means may be employed with the arrangement of Figure 7 Referring. to the drawings, and more particularly to Figures 1 to '3, I designates a conventional transmitter provided with the usual: components; such asan input, audio amplifier, an oscillator which generates the, carrier, a modulator for impressing the audio signal on the carrier, and an RF power output stage from which the modulated carrier is delivered to the antenna. Designated at 12 is a supersonic audio oscillator which connected to the audio circuit at the in put portion of the transmitter through a control switch 13, so. that when switch 13 cio'se'd, output of oscillator i2 is impressed on the carrier, along w ith the speech 'or music program modulations. The frequency or oscillator M is controlled by is tuned circuit which includes in parallel on inductance Hand-any *oneJor different-valued of the oscillator i2.

'gized. Said relay coil is capacitors i5 to ill, selection of one of said capacitors being accomplished by means of a punched card 2c which is inserted between spring contacts, shown diagrammatically at 2 I, 22, the card 28 being formed with an aperture through which a desired set of spring contacts 2 i, 22 may engage each other, as shown in Figure 1. The contacts 2i are respectively connected to one terminal of the respective tuning capacitors 65 to l9, whereas the contacts 22 are connected to one terminal of the inductance M, the other terminal of the inductance being connected to the opposite terminals of the tuning capacitors. The frame of the apparatus is provided with suitable receiving means, not shown, for the card 29, said receiving means being provided with stops arranged to suitably locate the card so that connection of a desired tuning capacitor to th inductance will occur by the interengagement of the corresponding contacts 2|, 22 through the aperture in the card when said card is seated in the receiving means. By substituting another card 2|) having its aperture located difierently, a different tuning capacitor may be connected to the inductance i l, thereby changing the frequency The frequency of the oscilreadily changed by changing the punched cards 20. In the typical arrangement of Figure 1, there may be five different punched cards, the aperture of each card being located so as to align with a different set of spring contacts 2|, 22 when the card is seated in the receiving means. Thus, the oscillator l2 may have any one of five different supersonic audio lator l2 may thus be frequencies.

a receiving arrangement adapted to respond to the signals produced by the arrangement of Figure '1 may comprise a conventional receiver 23 whose audio output is connected to the voice coil of a loud speaker 24 through relay contacts 25, 26, said contacts being normally closed, but being opened when the relay coil, shown at 21, becomes enerconnected in the plate circuit of a triode 28. Designated at 29 is a tuned audio circuit whose input circuit is convnected to the audio output circuit of receiver 23 ahead of the contacts 25, 25. The resonant frequency of the tuned circuit 29 is controlled by a parallel tuning circuit comprising an inductance -30 and any one of a plurality of different-valued capacitors 3! to 35. Selection of a tuning capacitor is accomplished by a punched card 36 similar to the punched card 20 at the transmitter.

The punched card 36 is inserted between spring contacts 31, 38, the respective contacts 31 being .each connected to one the respective capacitors ungrounded terminal of 3! to 35 and the contacts 38 being connected to the ungrounded terminal of the inductance Ed, said ungrounoled terminal being connected through an amplifier 39 to the grid 4% of triode 28. The card 36 is provided with locating means arranged so that connection of a desired tuning capacitor to the inductance 38 will occur by the engagement of the corresponding contacts 31, 38 through the aperture in the card 'that pole when said card is placed in its locating means. In the typical arrangement shown, there are five different cards, corresponding to the five cards available at the transmitter. When corresponding cards are employed at the transmitter and the receiver, the particular capacitor connected to inductance 36 will have a value such as to resonate the tuned circuit 29 to the particular frequency of the supersonic audio oscillator l2 at the transmitter. Triode 28 is biased so as to be non-conducting except when a peak signal is applied to grid 40. Such a signal is provided when switch is at the transmitter is closed. When triode 28 conducts, relay coil 21 becomes energized and opens contacts 25, 26, thereby opening the circuit of the loud speaker 24.

Therefore, loud speaker 24 is cut out during the blocking period, which may be the period during which advertising or other announcements undesired by the subscriber, are transmitted. During said period, the transmitter operator closes switch l3, thereby preventing the an nouncements from being reproduced at the special receiver.

The punched cards 20 and 36 are changed from time to time, thereby changing the frequency of the supersonic control signal and preventing non-subscribers from enjoying continuous free benefits from the system, assuming that such non-subscribers have located the frequency of one control signal and have inserted a speaker control circuit resonant thereto in their receivers.

Referring now to Figures 6, 7 and 8, a modified form of radio broadcasting and receiving system according to the present invention is illustrated, wherein a continuous supersonic signal may be impressed on the carrier along with the normal audio modulations. As shown in Figure 8, the supersonic signal comprises a background frequency 4! which is designated in Figure 8 as the masking frequency. During the blocking period, the masking frequency is replaced for short intermittent periods by pulses of a different supersonic frequency 42, designated as blocking pulses. At the end of the blocking period, the masking requency is replaced for a short interval by still another supersonic frequency 43, designated as the release pulse. The amplitude of the supersonic wave remains constant at all times, including the times when the blocking pulses 42 and the release pulse 43 are present.

Figure 7 discloses schematically a transmitter arrangement for producing the supersonic signal of Figure 8 and impressing said signal on a transmitter carrier. Designated at 44 is the masking pulse oscillator, which generates the background supersonic frequency 41. Designated at 45 is the blocking pulse oscillator, which generates a supersonic frequency 42 differing from the background frequency. Designated at 46 is the release pulse oscillator which generates the third supersonic frequency 43 of Figure 8.

Shown at 41 is a two-pole, three-position switch whose poles are designated respectively at 48 and 49. Associated with pole 48 are the respective stationary contacts 50, 5| and 52, and associated with the pole 49 are the respective stationary contacts 53, 54 and 55. It will be seen 18 is connected by a wire 56 through an amplifier 5". and a limiter 58 to the audio input circuit of the transmitter 59. The output of the masking oscillator 44 is connected by wires 60 and hi to the stationary switch contact 50. The output of the release oscillator 46 is connected by a wire 62 to the contact 5|.

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Designated at 63 is a One terminal of i he motor 53 is connected to one supply line wire 8!, as shown. The other terminal of the motor is connected by a wire '55 to the stationary -switch contact 55. The switch pole '49 is connected to the remaining supply linewire '56.

Coupied to the "shaft of the motor 63 is a commutator 5'1. Said commutator is provided with the "continuous slip rings 68 and 6'9, and with a discontinuous slip ring m which has located between its ends and insulated therefrom a very short contact segment 1|. Segment H is electrically connected to slip ring 68, and the discontinuous slip ring 10 is electrically connected to slip ring 69. A stationary brush 12 engages the periphery of "slip ring '10 and momentarily engages the segment '11 once during each revolunon of the commutator 67. As shown in Figure I, whom! is connected to a stationary brush 13 which "engages slip ring t9. Engaging the slip ring 88 is a stationary brush M which is connected by a wire 15 to the output of the blocking poiseosc'ill'ator #5.

Connected across the wires 65 and -54 is a remy f5 provided with an armature '17 which -engages "a contact 18 when the relay is energized. Armature 7! is connected by a wire 19 to wire 58. Contact "18 is "connected by a wire "80 to the brush 12.

When the switch poles "4-3 and '49 are in their normal positions, shown in Figure 7, motor 63 is 'deenergized and the output of the background oscillator 44 is -connected through wires Gil, 61, contact 50, pole E8, wire 56, amplifier 51 and limiter 53 to the audio input circuit of the transmitter 59. Assume now that th'epoles 4'8 and 49 are rotated to respectively engage the uppermost contacts 52 and 55. Motor 63 now becomes energized through "a circuit comprising line wire 64, the motor winding, wire 65, contact 55, pole 49 and line wire 66. At the same time, relay 16 becomes energized, since it is connected in parallel with the motor, and armature 11 engages contact 18, connecting brush 12 to the audio output wire 56. Motor 53 rotates commutator 61. While brush 12 engages split ring "[0, the output 01' the masking pulse oscillator 44 is connected to wire 56 by wire 68, brush l3, slip ring "89, split ring 10, brush 1-2, wire 80, armaturell and wire 19. Each time the short segment H is engaged bybrush 12, however, the output of the blocking pulse oscillator 45 is connected to wire 56, in place of the masking frequency, by wire 15, brush N, slip ring 68, segment 7|, brush '2, wire 80, armature 1-1 and wire 19. This provides the blockingpulses in Figure 8.

At the end of the blocking period, the operator rotates the poles 48, 49 to engage the respective intermediate contacts 5|, 54. This deenergizes motor 53 and relay 16, disconnecting brush :2 from wire 56 by the release of armature 11'. At the same time, the output of the release oscillator 46 is connected to wire 56 by wire 52, contact 51 and pole 48. This provides the release pulse 43 at the end of the blocking period in Figure 8.

After a short interval, the operator restores poles 48, '49 to their initial positions, shown in Figure 1, wherein the output of the masking oscillator 44 is again connected to wire 58 by wire 54 and pole 48. The release interval may be merely that involved in rotating the poles of the witch from contacts 52, '55 through contacts 5|, Nth-contacts 50, R.

the wcflhtors :15 and are preferably proprovide the release vided with punch-card frequency-selecting means such as employed witnthe oscillator is of Figure 1. Furthermore, a single punch card 8] having two apertures may be employed to simultaneously select the frequencies of both oscilla'tors -35 and '45, as shown in Figur 13.

Figure 5 illustrates a modified form of the arrangemen't of Figure 7, wherein a mixer '82 is employed in conjunction with the background oscillator 4'4 and the blocking pulse oscillator '35 to pulse '53. As shown in Figure 5 the output wires so and 15 are connected to the input grids of the mixer 82 by respective wires 433 and 8-4. "The output wire 850f the mixer is connected to the switch contact 51. Hence, a heterodyne frequency of the background and blocking frequencies will be furnished to output wire 56 when pole 48 engages contact 51.

In Figure 5, a punched card irequency-seledting arrangement is provided for the blocking pulse oscillator 45, similar to that provided for the oscillator i2 of Figure '1. The punched card, shown 'at 86, may be readily changed to thereby vary the blocking pulse frequency and also the heterodyne frequency supplied by the mixer 82. In Figure 5, the background oscillator 4 4 is designated as providing, by way of example, a '30 kc. output frequency, and the punched card 88 apertured so as to select a frequency of 20 kc. for the "blocking pulse oscillator. The mixer 82 therefore provides beat frequencies of 50 kc. and 10 kc. As will be subsequently described, the receiver is arranged to respond to only one of the beat frequencies, for example, to the '50 kc. frequency, and hence, the 10 he. beat frequency will be ineffective and can be ignored. Figure 4 therefore may be considered as showing the nature of the effective supersonic signal provided on the transmitter carrier by the arrangement of Figure 5, immediately prior, during, and immedia'tely subsequent to the blocking period, produced by manipulation of the switch l-1 in the manner described in connection with Figure '7.

Merely by way of illustrating the relative time durations of the blocking pulse '42 and the intervenin'g background pulses -41 "during the blocking period, it is assumed that the commutator 6'! of Figure *5 rotates at a speed of 25 revolutions per second and that the brush 72 engages segment TI during a one-thousandth part of each revolution. The duration of the blocking pulse will therefore be of the order of 40 microseconds, and the time between successive blocking pulses will be .04 second, the background frequency being furnished during the time intervening between blocking pulses.

The speed of rotation of the commutator should be such that the average frequency of the blocking pulses is below the audible range, i. e, below about 3-0 cycles per second. It is "also very desirable to make the blocking pulses #2 occur in a non-periodic manner. One method of obtaining this result is to vary the speed of the motor 63 in 'a random fashion. This :may be accomplished by employing a motor having a variable speed control means, such as a speedcontrolling rheost-at, and by varying the setting of the rheostat manually during the period of energization of the motor. Another method of providing substantially random speed variation of the motor is to employ a motor having poor speed stability under load and to load the motor mechanically in an irregular manner, as il lustrated for example in Figures 11 and '12. The motor shaft, shown at '81, carries 'a "sleeve memher 88 making a relatively loose frictional fit with the shaft, the friction between the sleeve and the shaft, however, being sufificiently great to retard the motor when rotation of the sleeve is retarded by an external load. Sleeve 88 carries an eccentric 89. Engaging the periphery of eccentric 89 is a friction shoe 90 connected to an adjacent stationary support 9| by a link rod 92. A spring 93 connects rod 92 to th support 9I, providing variable braking force on the eccentric 89 as the eccentric is rotated by its frictional coupling with shaft 81. A substantially random retarding load is therefore applied to the motor shaft, causing the speed of the motor to vary in an irregular manner.

A still further method of making the blockin pulses 42 occur in a substantially non-periodic manner is to employ a commutator such as is shown in Figure 9, preferably in conjunction with a motor having poor stability. The commutator of Figur 9 is provided with a plurality of large segments 94 to 91, having different lengths, said large segments being each electrically connected to the slip ring 59. Between the ends of adjacent large segments are the very small segments 98, each connected to the slip ring 68. Figure 9 illustrates the angular displacement between successive small segments 98 in a typical arrangement. Figure 8 diagrammatically illustrates the sequence of blocking pulses 42 obtained by employing the commutator arrangement of Figure 9.

In the arrangement of Figure 9, the rotational speed of the commutator should be low enough to make the average frequency of the blocking pulses 42 subsonic.

Referring now to Figure 6, a receiver arrangement is disclosed adapted to respond to the control signals obtained from the transmitter arrangements of Figure 5 or '7, iwth or without the modifications disclosed by Figures 9, l1 and 12. Designated at 23 is a conventional receiver whose audio output is connected by wires I and IOI to the voice coil of a loud speaker 24 through relay contacts I02, I03, said relay contacts being normally closed but being opened when the relay I04 becomes energized. Said relay I04 is connected in the plate circuit of a gas triode I05, and included in said plate circuit are the normally closed contacts I05, I01 of another relay I08. Relay I08 is connected in the plate circuit of a triode I09, the triode I09 being biased so as to be normally non-conducting, whereby relay I08 is normally deenergized. Triode I09 conducts only when a substantially high-level signal is applied to its grid IIO.

Designated at III and H2 are respective tuned circuits whose input terminals are respectively connected to the audio output wires I00 and IOI of the receiver 23. Circuit III is tuned by a parallel tuning circuit comprising an inductance H3 and any one of a plurality of differentlyvalued capacitors II4, which are selected by a punched card II5, similar to the punched card ill of Figure 13. The punchard card I I5 is adapted to select a capacitor II4 suitable for resonating circuit III to the supersonic frequency of the blocking pulses 42. The ungrounded output terminal of tuned circuit III is connected by a wire H0 through an amplifier II1 to the grid II8 of the gas triode I05. When blocking pulses 42 are present in the audio output of receiver 23, a signal of high amplitude is applied to grid II8, causing tube I05 to fire. This energizes relay I04, opening the loud speaker circuit at contacts I02, I03.

Circuit I I2 is tuned by a parallel tuning circuit comprising an inductance H9 and any one of a plurality of different-valued capacitor I20, which are selected by the punched card I I5. Card H5 is adapted to select a capacitor I20 suitable for resonating circuit II2 to the supersonic frequency of the release pulse 43. The ungrounded output terminal of tuned circuit H2 is connected by a wire I2I through an amplifier I22 to the grid IIO of the triode I09. When a release pulse 43 is present in the audio output of receiver 23, a high-amplitude signal is applied to grid IIO, causing tube I09 to conduct.

At the beginning of the blocking period, tube I05 is triggered into conduction, causing relay I04 to open contacts I02, I03, deenergizing the loud speaker 24. Relay I04 remains energized throughout the blocking period, since tube I05 continues to conduct. At the end of the blocking period, a release pulse 43 causes triode I09 to conduct, thereby energizing relay I08, opening the plate circuit of gas triode I05 at contacts I08, I01. At the termination of the release pulse 43, gas triode I05 remains non-conducting, since no further triggering pulses 42 are present in the audio output of receiver 23. Therefore contacts I02, I03 remain closed, restoring the continuity of the loud speaker voice coil circuit.

It will be understood that in either of the receiver arrangements of Figures 3 or 6, the circuit to be controlled may be any circuit which will deenergize the reproducing portion of the receiver when opened, and the present invention is not limited to control only of the loud speaker voice coil circuits.

It is also further contemplated that the twopole, three-position switch 41 employed in Figures 5 and 'I may be of the continuously rotatable type, whereby poles 48, 49 may be rotated from engagement with contacts 50, 53 to engagement with contacts 52, 55 without engaging the contacts 5|, 54 when the blocking period is initiated, thereby preventing the transmission of a release pulse 43 at the beginning of the blocking period.

While certain specific embodiments of an improved system for separating entertainment programs from speech, such as advertising and the like, in radio and television transmission and reception have been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined .by the scope of the appended claims.

What is claimed is:

1. In combination with a radio transmitter, a first oscillator adapted to produce a signal of a first supersonic audio frequency, a second oscillator adapted to produce a signal of supersonic audio frequency, a tuned circuit associated with said second oscillator in frequency-controlling relationship therewith, said tuned circuit including a first reactance, a plurality of additional reactances, means for selectively connect ing said additional reactances to said first reactance, said means comprising opposing switch contacts connected respectively to said first reactance and to each of the additional reactances, and a card formed with a perforation, said card being receivable between said opposing switch contacts with said perforation in registry with one set of opposing contacts, whereby a selected one of said additional reactances is connected to said first reactance, a cyclically driven mechanical switch connected between said oscillators and said transmitter, means on said switch for alternately connecting the oscillators to the transmitter, means providing a signal of a third supersonic audio frequency, multiple-position mechanical switch means, circuit means connecting said cyclically driven mechanical switch to the transmitter when said multiple-position switch means is in a first position, additional circuit means selectively connecting said first oscillator or said third named means to said transmitter when the multiple-position switch means is in other positions, and means disconnecting said cyclically driven mechanical switch from the transmitter when said multiple-position switch means is in any one of said other positions.

2. The structure of claim 1, and limiter connected between said cyclically driven switch and the transmitter.

3. The structure of claim 1, and wherein said cyclically driven switch comprises a rotating commutator having two segments, one connected to each oscillator, and a stationary brush element alternately engageable with said segments and connected to the transmitter.

an amplitude 10 4. The structure of claim 3, and wherein the segment connected to the first oscillator is relatively long and the segment connected to the second oscillator is relatively short.

LEVERING H. GILPIN. HERMAN L. GORDON.

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